Natural population growth rate
Natural growth rate of population and the demographic transition
Of the three factors (fertility, mortality, and international migration) that determine population size of a country, the two (fertility or birth rate and mortality or death rate) determine natural growth of the population. Comparative variation in magnitude of these two variables over a long term which is called as demographic transition, characterize the population to be with high birth rate and high death rate at one end to low death rate and low birth rate at the other end. There are two other characteristics in between. The four stages of these characteristics are:
* The first stage of demographic change is the time when both the birth rate and death rate fluctuate and are quite high. This is the period when the natural growth rate of population is quite low.
* The second stage of transition is when the death rate starts to decline while birth rate remains more or less constant. This is the period when the population growth rate starts to increase and reaches the maximum.
* At the third stage, birth rate also starts to decline as a response to declining death rate.
* Finally the fourth stage is when birth rate and death rate are quite close and birth rate is close to replacement level and fluctuates. At this, the natural growth of population either stops or decrease. Countries in this stage often tend to balance the population size through immigration of some international migrant population.
Demographic balance often a long term goal can be achieved when the birth rate of a population equals the death rate i.e. when replacement level is met and rate is stable. .
Situation in SEAR
With fast decline in birth rates along with death rates, almost all SEAR countries seem to be entering in the third stage of the demographic transition.
As shown in the graph, from 1990 to 2010, decline in both the crude death rates CDR) and the crude birth rates (CBR) were higher than the world average in eight of the SEAR countries. While four out of these eight countries ( Maldives, Bhutan, Bangladesh, and Nepal) had higher decline in crude death rates, two (Myanmar and India) had higher decline in crude birth rates. The other two countries (Thailand and DPR Korea) however had negative decline in crude death rates (meaning crude death rates in these countries were higher in 2010 than what was in 1990 and could have been due to increasing percentage of old people) . Of the remaining three countries (Indonesia, Sri Lanka, and Timor-Leste), Indonesia had equal decline in CDR and CBR (meaning population size getting stabilized), Sri Lanka had no change in CDR but had decline in CBR (meaning population heading for decline), Timor-Leste with its already high level of birth rate had decline in it at only one fifth of the decline in death rate (meaning decline in population growth rate is mostly due to increasing death rate instead of decline in birth rate).
(Note : Birth rate and death rate computed normally dividing total births or deaths in a year by midyear population are called crude rates because these rates are for total population and do not take into account the effect of age and sex differences in the population).